Compositions and processes for immersion lithography

ABSTRACT

New photoresist compositions are provided that are useful for immersion lithography. Preferred photoresist compositions of the invention comprises two or more distinct materials that can be substantially non-mixable with a resin component of the resist. Particularly preferred photoresists of the invention can exhibit reduced leaching of resist materials into an immersion fluid contacting the resist layer during immersion lithography processing.

The present application is a Continuation of U.S. Non-ProvisionalApplication Ser. No. 12/290,980, filed Nov. 5, 2008 now U.S. Pat. No.8,257,902, which application claims the benefit of priority of U.S.Provisional Application No. 61/001,884, filed Nov. 5, 2007, the entirecontents of which application is incorporated herein by reference.

The present invention relates to new photoresist compositions that areparticularly useful in immersion lithography processes. Preferredphotoresist compositions of the invention comprises two or morematerials that can be substantially non-mixable with a resin componentof the resist. Particularly preferred photoresists of the invention canexhibit reduced leaching of resist materials into an immersion fluidcontacting the resist layer during immersion lithography processing.

Photoresists are photosensitive films used for transfer of an image to asubstrate. A coating layer of a photoresist is formed on a substrate andthe photoresist layer is then exposed through a photomask to a source ofactivating radiation. The photomask has areas that are opaque toactivating radiation and other areas that are transparent to activatingradiation. Exposure to activating radiation provides a photoinducedchemical transformation of the photoresist coating to thereby transferthe pattern of the photomask to the photoresist coated substrate.Following exposure, the photoresist is developed to provide a reliefimage that permits selective processing of a substrate.

The growth of the semiconductor industry is driven by Moore's law whichstates that the complexity of an IC device doubles on average every twoyears. This necessitates the need to lithographically transfer patternsand structures with ever decreasing feature size.

One approach to achieving smaller feature sizes is to use shorterwavelengths of light, however, the difficulty in finding materials thatare transparent below 193 nm has led to the option of using immersionlithography to increase the numerical aperture of the lens by simplyusing a liquid to focus more light into the film. Immersion lithographyemploys a relatively high refractive index fluid between the lastsurface of an imaging device (e.g., KrF or ArF stepper) and the firstsurface on a wafer or other substrate.

Certain efforts have been made to address problems associated withimmersion lithography. See U.S. Patent Application Publication2006/0246373. Additional reliable and convenient photoresist and imagingprocesses for immersion lithography are clearly needed.

It would be desirable to new materials and processes for immersionphotolithograpy.

We now provide new compositions and processes for immersionphotolithography.

Preferred photoresists of the invention may comprise:

(i) one or more resins,

(ii) a photoactive component which may suitably comprise one or morephotoacid generator compounds, and

(iii) two or more distinct materials that are substantially non-mixablewith the one or more resins.

Of such photoresist compositions preferred are chemically-amplifiedpositive-acting resists, e.g. where the resin component comprises one ormore resins comprising photoacid-labile groups such as photoacid-labileester or acetal groups.

The substantially non-mixable component of such photoresist compositionssuitably comprises at least two distinct materials. Those distinctmaterials sometimes may be referred to herein as a “top material” and“intermediate material”. Preferred top and intermediate materials arepolymers (resins) which may suitably differ by at least one polymerrepeat unit.

In preferred systems, the top material and intermediate material alsodiffer in hydrophobicity, particularly where the top material is morehydrophobic than the intermediate material. Thus, for example, theintermediate material may contain more polar groups (relative to the topmaterial) to the polar group where such polar groups may suitablycontain one or more hetero atoms (O, N, S) such as hydroxy, haloalcohol(e.g. —CH(OH)(CF₃)₂), carboxy (—COOH)), ester (—C(═O)OR where R is C₁₋₂₀alkyl), sulfono (—SO₃H), and ether. For instance, the top materialmaterial and intermediate material by be the same general resins, exceptone repeat unit of the intermediate material may contain haloalcohol(e.g. —CH(OH)(CF₃)₂) substitution whereas the corresponding unit of thetop material does not contain such halalcohol substitution.

In additional preferred systems, the intermediate material also maydiffer in hydrophobicity relative to the resin component of thephotoresist composition, particularly where the intermediate material ismore hydrophobic than the resin component (again, inchemically-amplified positive-acting resists, the resin componentcomprises one or more resins that comprise photoacid-labile groups).Thus, for instance, the one or more resins may comprise more (relativeto the intermediate material as well as the top material) polar groupssuch as ester or acetal groups (which may be photoactive) or other polargroups which may suitably contain one or more hetero atoms (O, N, S)such as hydroxy, haloalcohol (e.g. —CH(OH)(CF₃)₂) carboxy (—COOH)),sulfono (—SO₃H), and ether.

In such preferred photoresist systems, in addition to differences inhydrophobicity, preferably the surface energy of the top material isgreater than the surface energy of the intermediate material Furtherpreferred is where the surface energy of the intermediate material isgreater than the surface energy of the resin component (again, inchemically-amplified positive-acting resists, the resin componentcomprises one or more resins that comprise photoacid-labile groups). Forinstance, the surface energy between the top material and theintermediate material may differ by at least about 5, 10, 15, 20 or 25dynes/cm. Similarly, the surface energy between the intermediatematerial and the resin component may differ by at least about 5, 10, 15,20 or 25 dynes/cm.

In such preferred systems, by such differences in hydrophobicity andsurface energy, a spin-coated layer of the photoresist composition mayadapt a graded configuration, wherein a substantial portion of the resincomponent (again, in chemically-amplified positive-acting resists, theresin component comprises one or more resins that comprisephotoacid-labile groups) will be closer to the underlying substratesurface relative to the intermediate and top materials, and asubstantial portion of the intermediate material will be closer to theunderlying substrate surface than the top material in the photoresistcomposition layer. References to “substantial portion(s)” of a topmaterial, intermediate material or resin component herein are intendedto indicate at least 30, 40, 50, 60 or 70 weight percent of thatmaterial or component, based on total weight of that material orcomponent in the photoresist composition.

Particularly preferred photoresists of the invention can exhibit reducedmigration (leaching) of photoresist components into the immersion fluidduring contact of the immersion fluid during an exposure step.Significantly, such reduced migration of photoresist materials intoimmersion fluid can be achieved without applying any type of cover orbarrier layer over the photoresist and interposed between the resistlayer and immersion fluid.

We have found that undesired migration of acid and/or other resistmaterials from a photoresist layer into the immersion fluid layer can beparticularly problematic. Among other things, the acid or otherphotoresist materials that migrate into the immersion fluid can damagethe exposure tool as well as reduce resolution of an image patternedinto a photoresist layer. Accordingly, the photoresists of the inventionconstitute a significant advance.

Without being bound by any theory, it is believed the two or moredistinct materials that are substantially non-mixable with the one ormore resist resins can migrate toward upper regions of an appliedphotoresist coating layer and thereby inhibit migration of photoresistmaterials out of a resist layer into immersion fluid that contacts theresist layer during an immersion exposure step.

Additionally, by use of multiple non-mixable materials, it is possibleto control multiple lithographic properties of a photoresistcomposition. For instance, the top material of a photoresist compositioncan provide an optimal water contact angle to facilitate interactionswith overcoating fluid in an immersion lithography process. Theintermediate material then can serve as a primary barrier to avoidleaching. The use of the two distinct materials (i.e. top andintermediate materials) together also can provide more effective controlof undesired leaching of photoresist component(s) into overcoatingimmersion fluid.

As referred to herein, materials that are substantially non-mixable withthe one or more photoresist resins include those materials added to aphotoresist that results in reduced migration or leaching of photoresistmaterials into immersion fluid. Such substantially non-mixable materialscan be readily identified empirically by testing relative to a controlresist that has the same components as the tested photoresist, but notthe candidate substantially non-mixable material(s).

Suitable substantially non-mixable materials for use in photoresists ofthe invention include compositions that comprise silicon and/or fluorinesubstitution.

Preferred substantially non-mixable materials for use in photoresists ofthe invention may be in the form of particles. Such particles mayinclude polymers that are polymerized in the form discrete particles,i.e. as separate and distinct polymer particles. Such polymer particlestypically have one or more different characteristics from linear orladder polymers such as linear or ladder silicon polymers. For example,such polymer particles may have a defined size and a low molecularweight distribution. More particularly, in a preferred aspect, aplurality of the polymer particles may be employed in a photoresist ofthe invention with a mean particle size (dimension) of from about 5 to3000 angstroms, more preferably from about 5 to 2000 angstroms, stillmore preferably from about 5 to about 1000 angstroms, yet morepreferably from about 10 to about 500 angstroms, even more preferablyfrom 10 to 50 or 200 angstroms. For many applications, particularlypreferred particles have a mean particle size of less than about 200 or100 angstroms.

Additional preferred substantially non-mixable materials for use inphotoresists of the invention may have Si content, includingsilsesquioxane materials, materials with SiO₂ groups, and the like.Preferred silicon-containing substantially non-mixable materials alsoinclude polyhedral oligomeric silsesquioxanxes.

Also preferred are those substantially non-mixable materials thatcontain photoacid-labile groups, such as photoacid-labile ester oracetal groups, including such groups as described herein employed in aresin component of a chemically amplified photoresist.

Preferred substantially non-mixable materials for use in photoresists ofthe invention also will be soluble in the same organic solvent(s) usedto formulate the photoresist composition.

Particularly preferred substantially non-mixable materials for use inphotoresists of the invention also will have lower surface energy and/orsmaller hydrodynamic volume than the one or more resins of thephotoresist's resin component. The lower surface energy can facilitatesegregation or migration of the substantially non-mixable materials totop or upper portions of an applied the photoresist coating layer.Additionally, relative smaller higher hydrodynamic volume also can bepreferred because it can facilitate efficient migration (higherdiffusion coefficient) of the one or more substantially non-mixablematerials to upper regions of the applied photoresist coating layer.

Preferred substantially non-mixable materials for use in photoresists ofthe invention also will be soluble in photoresist developer compositions(e.g. 0.26N aqueous alkaline solution). Thus, in addition tophotoacid-labile groups as discussed above, other aqueousbase-solubilizing groups may be included in the substantiallynon-mixable materials such as hydroxyl, fluoroalcohol, carboxy and thelike.

Preferred imaging wavelengths of lithographic systems of the inventioninclude sub-400 nm such as I-line (365 nm), sub-300 nm wavelengths e.g.248 nm, and sub-200 nm wavelengths e.g. 193 nm. In addition to one ormore substantially non-mixable materials, particularly preferredphotoresists of the invention may contain a photoactive component (e.g.one or more photoacid generator compounds) and one or more resins thatare chosen from among:

1) a phenolic resin that contains acid-labile groups that can provide achemically amplified positive resist particularly suitable for imagingat 248 nm. Particularly preferred resins of this class include: i)polymers that contain polymerized units of a vinyl phenol and an alkylacrylate, where the polymerized alkyl acrylate units can undergo adeblocking reaction in the presence of photoacid. Exemplary alkylacrylates that can undergo a photoacid-induced deblocking reactioninclude e.g. t-butyl acrylate, t-butyl methacrylate, methyladamantylacrylate, methyl adamantyl methacrylate, and other non-cyclic alkyl andalicyclic acrylates that can undergo a photoacid-induced reaction, suchas polymers in U.S. Pat. Nos. 6,042,997 and 5,492,793, incorporatedherein by reference; ii) polymers that contain polymerized units of avinyl phenol, an optionally substituted vinyl phenyl (e.g. styrene) thatdoes not contain a hydroxy or carboxy ring substituent, and an alkylacrylate such as those deblocking groups described with polymers i)above, such as polymers described in U.S. Pat. No. 6,042,997,incorporated herein by reference; and iii) polymers that contain repeatunits that comprise an acetal or ketal moiety that will react withphotoacid, and optionally aromatic repeat units such as phenyl orphenolic groups; such polymers have been described in U.S. Pat. Nos.5,929,176 and 6,090,526, incorporated herein by reference, as well asblends of i) and/or ii) and/or iii);

2) phenolic resins that do not contain acid-labile groups such aspoly(vinylphenol) and novolak resins that may be employed in I-line andG-line photoresists together with a diazonaphthoquinone photoactivecompound and have been described e.g. in U.S. Pat. Nos. 4,983,492;5,130,410; 5,216,111; and 5,529,880;

3) a resin that is substantially or completely free of phenyl or otheraromatic groups that can provide a chemically amplified positive resistparticularly suitable for imaging at sub-200 nm wavelengths such as 193nm. Particularly preferred resins of this class include: i) polymersthat contain polymerized units of a non-aromatic cyclic olefin(endocyclic double bond) such as an optionally substituted norbornene,such as polymers described in U.S. Pat. Nos. 5,843,624, and 6,048,664,incorporated herein by reference; ii) polymers that contain alkylacrylate units such as e.g. t-butyl acrylate, t-butyl methacrylate,methyladamantyl acrylate, methyl adamantyl methacrylate, and othernon-cyclic alkyl and alicyclic acrylates; such polymers have beendescribed in U.S. Pat. No. 6,057,083; European Published ApplicationsEP01008913A1 and EP00930542A1; and U.S. pending patent application Ser.No. 09/143,462, all incorporated herein by reference, and iii) polymersthat contain polymerized anhydride units, particularly polymerizedmaleic anhydride and/or itaconic anhydride units, such as disclosed inEuropean Published Application EP01008913A1 and U.S. Pat. No. 6,048,662,both incorporated herein by reference, as well as blends of i) and/orii) and/or iii);

4) a resin that contains repeat units that contain a hetero atom,particularly oxygen+ and/or sulfur (but other than an anhydride, i.e.the unit does not contain a keto ring atom), and preferable aresubstantially or completely free of any aromatic units. Preferably, theheteroalicyclic unit is fused to the resin backbone, and furtherpreferred is where the resin comprises a fused carbon alicyclic unitsuch as provided by polymerization of a norborene group and/or ananhydride unit such as provided by polymerization of a maleic anhydrideor itaconic anhydride. Such resins are disclosed in PCT/US01/14914 andU.S. application Ser. No. 09/567,634.

5) resins that contain Si-substitution including poly(silsequioxanes)and the like and may be used with an undercoated layer. Such resins aredisclosed e.g. in U.S. Pat. No. 6,803,171.

6) a resin that contains fluorine substitution (fluoropolymer), e.g. asmay be provided by polymerization of tetrafluoroethylene, a fluorinatedaromatic group such as fluoro-styrene compound, compounds that comprisea hexafluoroalcohol moiety, and the like. Examples of such resins aredisclosed e.g. in PCT/US99/21912.

Preferred photoresists of the invention include bothchemically-amplified positive-acting and negative-acting photoresists.Typically preferred chemically-amplified positive resists include one ormore resins that comprise photoacid-labile groups such asphotoacid-labile ester or acetal groups.

The invention further provides methods for forming a photoresist reliefimage and producing an electronic device using photoresists of theinvention. The invention also provides novel articles of manufacturecomprising substrates coated with a photoresist composition of theinvention.

Other aspects of the invention are disclosed infra.

FIG. 1 shows schematically a preferred photoresist composition layer ofthe invention.

We have found that addition of two or more distinct substantiallynon-mixable materials can improve lithographic performance of aphotoresist.

Preferred photoresists of the invention comprises at least threedistinct resins: a first resin that comprises photoacid labile groupsand distinct second and third resins. Each of the resins preferablydiffer in hydrophobicity and surface energy as discussed above.Hydrophobicity and surface energy may be assessed by known methods. Forexample, U.S. Pat. No. 6,927,012 discloses methods for determination ofsurface energy of a material. Hydrophobicity of a material can beassessed by high performance liquid chromographic methods. Each of thefirst resin that comprises photoacid labile groups and distinct secondand third resins may have a molecular weight within a wide range, e.g. aMw of from about 1,000 to 100,000, more typically an Mw of 1500 to8,000, 10,000, 15,000, 20,000, 30,000, 40,000 or 50,000, with apolydispersity of about 4, 3 or 2 or less.

Referring to FIG. 1, there is shown a schematic of a preferredphotoresist composition 10 that has been spin-coated onto a siliconwafer 12. The applied photoresist composition layer has been soft-baked(e.g. 105° C. for 60 seconds) to remove solvent. As shown in FIG. 1,materials of the photoresist can segregate into differing regions, i.e.wherein the one or more resins with photoacid labile groupssubstantially reside in area 14 closest to the surface of substrate 12,followed by the intermediate material (e.g. terpolymer withhexafluoroalcohol and carboxy groups) which may substantially reside inthe depicted intermediate region 16, and then top polymer (e.g.copolymer with less polar groups than the intermediate material) whichmay substantially reside in the depicted top region 18.

As discussed above, suitable materials of photoresists of the inventionthat are substantially non-mixable with the resist resin component canbe readily identified by simple testing. In particular, as referred toherein, preferred substantially non-mixable materials will provide adecreased amount of acid or organic material to be detected in theimmersion fluid upon use of the photoresist composition containing thecandidate material relative to the same photoresist system that isprocessed into the same manner, but in the absence of the candidatesubstantially non-mixable material(s). Detection of photoresist materialin the immersion fluid can be conducted as described in Example 2 whichfollows and includes mass spectroscopy analysis of the immersion fluidbefore and after exposure to the photoresist. In such analysis, theimmersion fluid directly contacts the tested photoresist compositionlayer for about 60 seconds during exposure. Preferably, addition of oneor more substantially non-mixable materials provides at least a 10percent reduction in photoresist material (again, acid or organics asdetected by mass spectroscopy) residing in the immersion fluid relativeto the same photoresist that does not employ such substantiallynon-mixable material(s), more preferably the one or more substantiallynon-mixable materials provides at least a 20, 50, or 100, 200, 500, or1000 percent reduction photoresist material (again, acid and/ororganics) residing in to the immersion fluid relative to the samephotoresist that does not contain the substantially non-mixablematerial(s).

As discussed above, specifically preferred substantially non-mixablematerials include Si-containing materials. Especially preferredsubstantially non-mixable materials include nanostructured compositions,which are commercially available from groups such as Hybrid Plastics(Fountain Valley, Calif.), Sigma/Aldrich, and others. Such materials mayinclude molecular silicas which have a Si—O core enveloped by organicgroups; silanols; and polymers and resins which include silsesquioxanecage-structured compounds and may be silicones, styrenics, acrylics,alicyclics such as norbornenes and others.

Particles (including organic particles) useful as substantiallynon-mixable materials include Si-containing and fluorinated materials.Such particles are commercially available, or can be readilysynthesized, e.g. by reaction of one or more monomers together with acrosslinking agent and an initiator compound if desired. The reactedmonomers may have substitution as desired e.g. fluorine, Si groups,photoacid-labile groups such as photoacid-labile esters or acetals,other base-solubilizing groups such as alcohols and the like. SeeExample 1 which follows for an exemplary synthesis of such particlesproduced with multiple distinct monomers, where one of the monomersprovides a photoacid-labile group to the resulting polymer particle.

The substantially non-mixable material(s) may be present in aphotoresist composition in relatively small amounts and still provideeffective results. For instance, the one or more substantiallynon-mixable materials may be suitable present in about 0.1 to 20 weightpercent based on total weight of a fluid photoresist composition.Suitable amounts also are provided in the examples which follow.

As discussed above, preferred photoresists for use in accordance withthe invention include positive-acting or negative-acting chemicallyamplified photoresists, i.e. negative-acting resist compositions whichundergo a photoacid-promoted crosslinking reaction to render exposedregions of a coating layer of the resist less developer soluble thanunexposed regions, and positive-acting resist compositions which undergoa photoacid-promoted deprotection reaction of acid labile groups of oneor more composition components to render exposed regions of a coatinglayer of the resist more soluble in an aqueous developer than unexposedregions. Ester groups that contain a tertiary non-cyclic alkyl carbon(e.g. t-butyl) or a tertiary alicyclic carbon (e.g. methyladamantyl)covalently linked to the carboxyl oxygen of the ester are oftenpreferred photoacid-labile groups of resins employed in photoresists ofthe invention. Acetal photoacid-labile groups also will be preferred.

Preferred photoresists of the invention typically comprise a resincomponent and a photoactive component. Preferably the resin hasfunctional groups that impart alkaline aqueous developability to theresist composition. For example, preferred are resin binders thatcomprise polar functional groups such as hydroxyl or carboxylate.Preferably a resin component is used in a resist composition in anamount sufficient to render the resist developable with an aqueousalkaline solution.

For imaging at wavelengths greater than 200 nm, such as 248 nm, phenolicresins are typically preferred. Preferred phenolic resins arepoly(vinylphenols) which may be formed by block polymerization, emulsionpolymerization or solution polymerization of the corresponding monomersin the presence of a catalyst. Vinylphenols useful for the production ofpolyvinyl phenol resins may be prepared, for example, by hydrolysis ofcommercially available coumarin or substituted coumarin, followed bydecarboxylation of the resulting hydroxy cinnamic acids. Usefulvinylphenols may also be prepared by dehydration of the correspondinghydroxy alkyl phenols or by decarboxylation of hydroxy cinnamic acidsresulting from the reaction of substituted or nonsubstitutedhydroxybenzaldehydes with malonic acid. Preferred polyvinylphenol resinsprepared from such vinylphenols have a molecular weight range of fromabout 2,000 to about 60,000 daltons.

Also preferred for imaging at wavelengths greater than 200 nm, such as248 nm are chemically amplified photoresists that comprise in admixturea photoactive component and a resin component that comprises a copolymercontaining both phenolic and non-phenolic units. For example, onepreferred group of such copolymers has acid labile groups substantially,essentially or completely only on non-phenolic units of the copolymer,particularly alkylacrylate photoacid-labile groups, i.e. aphenolic-alkyl acrylate copolymer. One especially preferred copolymerbinder has repeating units x and y of the following formula:

wherein the hydroxyl group be present at either the ortho, meta or parapositions throughout the copolymer, and R′ is substituted orunsubstituted alkyl having 1 to about 18 carbon atoms, more typically 1to about 6 to 8 carbon atoms. Tert-butyl is a generally preferred R′group. An R′ group may be optionally substituted by e.g. one or morehalogen (particularly F, Cl or Br), C₁₋₈ alkoxy, C₂₋₈ alkenyl, etc. Theunits x and y may be regularly alternating in the copolymer, or may berandomly interspersed through the polymer. Such copolymers can bereadily formed. For example, for resins of the above formula, vinylphenols and a substituted or unsubstituted alkyl acrylate such ast-butylacrylate and the like may be condensed under free radicalconditions as known in the art. The substituted ester moiety, i.e.R′—O—C(═O)—, moiety of the acrylate units serves as the acid labilegroups of the resin and will undergo photoacid induced cleavage uponexposure of a coating layer of a photoresist containing the resin.Preferably the copolymer will have a M_(w) of from about 8,000 to about50,000, more preferably about 15,000 to about 30,000 with a molecularweight distribution of about 3 or less, more preferably a molecularweight distribution of about 2 or less. Non-phenolic resins, e.g. acopolymer of an alkyl acrylate such as t-butylacrylate ort-butylmethacrylate and a vinyl alicyclic such as a vinyl norbornanyl orvinyl cyclohexanol compound, also may be used as a resin binder incompositions of the invention. Such copolymers also may be prepared bysuch free radical polymerization or other known procedures and suitablywill have a M_(w) of from about 8,000 to about 50,000, and a molecularweight distribution of about 3 or less.

Other preferred resins that have acid-labile deblocking groups for usein a positive-acting chemically-amplified photoresist of the inventionhave been disclosed in European Patent Application 0829766A2 of theShipley Company (resins with acetal and ketal resins) and EuropeanPatent Application EP0783136A2 of the Shipley Company (terpolymers andother copolymers including units of 1) styrene; 2) hydroxystyrene; and3) acid labile groups, particularly alkyl acrylate acid labile groupssuch as t-butylacrylate or t-butylmethacrylate). In general, resinshaving a variety of acid labile groups will be suitable, such as acidsensitive esters, carbonates, ethers, imides, etc. The photoacid labilegroups will more typically be pendant from a polymer backbone, althoughresins that have acid labile groups that are integral to the polymerbackbone also may be employed.

As discussed above, for imaging at sub-200 nm wavelengths such as 193nm, preferably a photoresist is employed that contains one or morepolymers that are substantially, essentially or completely free ofphenyl or other aromatic groups. For example, for sub-200 nm imaging,preferred photoresist polymers contain less than about 5 mole percentaromatic groups, more preferably less than about 1 or 2 mole percentaromatic groups, more preferably less than about 0.1, 0.02, 0.04 and0.08 mole percent aromatic groups and still more preferably less thanabout 0.01 mole percent aromatic groups. Particularly preferred polymersare completely free of aromatic groups. Aromatic groups can be highlyabsorbing of sub-200 nm radiation and thus are undesirable for polymersused in photoresists imaged with such short wavelength radiation.

Suitable polymers that are substantially or completely free of aromaticgroups and may be formulated with a PAG of the invention to provide aphotoresist for sub-200 nm imaging are disclosed in European applicationEP930542A1 and U.S. Pat. Nos. 6,692,888 and 6,680,159, all of theShipley Company.

Suitable polymers that are substantially or completely free of aromaticgroups suitably contain acrylate units such as photoacid-labile acrylateunits as may be provided by polymerization of methyladamanatylacrylate,methyladamantylmethacrylate, ethylfenchylacrylate,ethylfenchylmethacrylate, and the like; fused non-aromatic alicyclicgroups such as may be provided by polymerization of a norbomene compoundor other alicyclic compound having an endocyclic carbon-carbon doublebond; an anhydride such as may be provided by polymerization of maleicanhydride and/or itaconic anhydride; and the like.

Preferred negative-acting compositions of the invention comprise one ormore materials (such as a crosslinker component e.g. an amine-basedmaterials such as a melamine resin) that will cure, crosslink or hardenupon exposure to acid, and a photoactive component of the invention.Particularly preferred negative acting compositions comprise a resinbinder such as a phenolic resin, a crosslinker component and aphotoactive component of the invention. Such compositions and the usethereof has been disclosed in European Patent Applications 0164248 and0232972 and in U.S. Pat. No. 5,128,232 to Thackeray et al. Preferredphenolic resins for use as the resin binder component include novolaksand poly(vinylphenol)s such as those discussed above. Preferredcrosslinkers include amine-based materials, including melamine,glycolurils, benzoguanamine-based materials and urea-based materials.Melamine-formaldehyde resins are generally most preferred. Suchcrosslinkers are commercially available, e.g. the melamine resins soldby American Cyanamid under the trade names Cymel 300, 301 and 303.Glycoluril resins are sold by American Cyanamid under trade names Cymel1170, 1171, 1172, urea-based resins are sold under the trade names ofBeetle 60, 65 and 80, and benzoguanamine resins are sold under the tradenames Cymel 1123 and 1125.

For imaging at sub-200 nm wavelengths such as 193 nm, preferrednegative-acting photoresists are disclosed in WO 03077029 to the ShipleyCompany.

Photoresists of the invention also may contain other materials. Forexample, other optional additives include actinic and contrast dyes,anti-striation agents, plasticizers, speed enhancers, sensitizers (e.g.for use of a PAG of the invention at longer wavelengths such as I-line(i.e. 365 nm) or G-line wavelengths), etc. Such optional additivestypically will be present in minor concentration in a photoresistcomposition except for fillers and dyes which may be present inrelatively large concentrations such as, e.g., in amounts of from 5 to30 percent by weight of the total weight of a resist's dry components.

A preferred optional additive of resists of the invention is an addedbase, e.g. a caprolactam, which can enhance resolution of a developedresist relief image. The added base is suitably used in relatively smallamounts, e.g. about 1 to 10 percent by weight relative to the PAG, moretypically 1 to about 5 weight percent. Other suitable basic additivesinclude ammonium sulfonate salts such as piperidinium p-toluenesulfonateand dicyclohexylammonium p-toluenesulfonate; alkyl amines such astripropylamine and dodecylamine; aryl amines such as diphenylamine,triphenylarnine, aminophenol,2-(4-aminophenyl)-2-(4-hydroxyphenyl)propane, etc.

The resin component of resists of the invention is typically used in anamount sufficient to render an exposed coating layer of the resistdevelopable such as with an aqueous alkaline solution. Moreparticularly, a resin binder will suitably comprise 50 to about 90weight percent of total solids of the resist. The photoactive componentshould be present in an amount sufficient to enable generation of alatent image in a coating layer of the resist. More specifically, thephotoactive component will suitably be present in an amount of fromabout 1 to 40 weight percent of total solids of a resist. Typically,lesser amounts of the photoactive component will be suitable forchemically amplified resists.

The resist compositions of the invention also comprise a photoacidgenerator (i.e. “PAG”) that is suitably employed in an amount sufficientto generate a latent image in a coating layer of the resist uponexposure to activating radiation. Preferred PAGs for imaging at 193 nmand 248 nm imaging include imidosulfonates such as compounds of thefollowing formula:

wherein R is camphor, adamantane, alkyl (e.g. C₁₋₁₂alkyl) andperfluoroalkyl such as perfluoro(C₁₋₁₂alkyl), particularlyperfluorooctanesulfonate, perfluorononanesulfonate and the like. Aspecifically preferred PAG isN-[(perfluorooctanesulfonyl)oxy]-5-norbornene-2,3-dicarboximide.

Sulfonate compounds are also suitable PAGs, particularly sulfonatesalts. Two suitable agents for 193 nm and 248 nm imaging are thefollowing PAGS 1 and 2:

Such sulfonate compounds can be prepared as disclosed in European PatentApplication 96118111.2 (publication number 0783136), which details thesynthesis of above PAG 1.

Also suitable are the above two iodonium compounds complexed with anionsother than the above-depicted camphorsulfonate groups. In particular,preferred anions include those of the formula RSO₃— where R isadamantane, alkyl (e.g. C₁₋₁₂ alkyl) and perfluoroalkyl such asperfluoro (C₁₋₁₂alkyl), particularly perfluorooctanesulfonate,perfluorobutanesulfonate and the like.

Other known PAGS also may be employed in photoresists used in accordancewith the invention. Particularly for 193 nm imaging, generally preferredare PAGS that do not contain aromatic groups, such as theabove-mentioned imidosulfonates, in order to provide enhancedtransparency.

Photoresists of the invention also may contain other optional materials.For example, other optional additives include anti-striation agents,plasticizers, speed enhancers, etc. Such optional additives typicallywill be present in minor concentrations in a photoresist compositionexcept for fillers and dyes which may be present in relatively largeconcentrations, e.g., in amounts of from about 5 to 30 percent by weightof the total weight of a resist's dry components.

The photoresists used in accordance with the invention are generallyprepared following known procedures. For example, a resist of theinvention can be prepared as a coating composition by dissolving thecomponents of the photoresist in a suitable solvent such as, e.g., aglycol ether such as 2-methoxyethyl ether (diglyme), ethylene glycolmonomethyl ether, propylene glycol monomethyl ether; propylene glycolmonomethyl ether acetate; lactates such as ethyl lactate or methyllactate, with ethyl lactate being preferred; propionates, particularlymethyl propionate, ethyl propionate and ethyl ethoxy propionate; aCellosolve ester such as methyl Cellosolve acetate; an aromatichydrocarbon such toluene or xylene; or a ketone such as methylethylketone, cyclohexanone and 2-heptanone. Typically the solids content ofthe photoresist varies between 5 and 35 percent by weight of the totalweight of the photoresist composition. Blends of such solvents also aresuitable.

Liquid photoresist compositions may be applied to a substrate such as byspinning, dipping, roller coating or other conventional coatingtechnique. When spin coating, the solids content of the coating solutioncan be adjusted to provide a desired film thickness based upon thespecific spinning equipment utilized, the viscosity of the solution, thespeed of the spinner and the amount of time allowed for spinning.

Photoresist compositions used in accordance with the invention aresuitably applied to substrates conventionally used in processesinvolving coating with photoresists. For example, the composition may beapplied over silicon wafers or silicon wafers coated with silicondioxide for the production of microprocessors and other integratedcircuit components. Aluminum-aluminum oxide, gallium arsenide, ceramic,quartz, copper, glass substrates and the like are also suitablyemployed. Photoresists also may be suitably applied over anantireflective layer, particularly an organic antireflective layer.

Following coating of the photoresist onto a surface, it may be dried byheating to remove the solvent until preferably the photoresist coatingis tack free.

The photoresist layer (with overcoated barrier composition layer, ifpresent) in then exposed in an immersion lithography system, i.e. wherethe space between the exposure tool (particularly the projection lens)and the photoresist coated substrate is occupied by an immersion fluid,such as water or water mixed with one or more additives such as cesiumsulfate which can provide a fluid of enhanced refractive index.Preferably the immersion fluid (e.g., water) has been treated to avoidbubbles, e.g. water can be degassed to avoid nanobubbles.

References herein to “immersion exposing” or other similar termindicates that exposure is conducted with such a fluid layer (e.g. wateror water with additives) interposed between an exposure tool and thecoated photoresist composition layer.

The photoresist composition layer is then suitably patterned exposed toactivating radiation with the exposure energy typically ranging fromabout 1 to 100 mJ/cm², dependent upon the exposure tool and thecomponents of the photoresist composition. References herein to exposinga photoresist composition to radiation that is activating for thephotoresist indicates that the radiation is capable of forming a latentimage in the photoresist such as by causing a reaction of thephotoactive component (e.g. producing photoacid from the photoacidgenerator compound).

As discussed above, photoresist compositions are preferablyphotoactivated by a short exposure wavelength, particularly a sub-400nm, sub-300 and sub-200 nm exposure wavelength, with I-line (365 nm),248 nm and 193 nm being particularly preferred exposure wavelengths aswell as EUV and 157 nm.

Following exposure, the film layer of the composition is preferablybaked at temperatures ranging from about 70° C. to about 160° C.Thereafter, the film is developed, preferably by treatment with anaqueous based developer such as quaternary ammonium hydroxide solutionssuch as a tetra-alkyl ammonium hydroxide solution; various aminesolutions preferably a 0.26N tetramethylammonium hydroxide, such asethyl amine, n-propyl amine, diethyl amine, di-n-propyl amine, triethylamine, or methyldiethyl amine; alcohol amines such as diethanol amine ortriethanol amine; cyclic amines such as pyrrole, pyridine, etc. Ingeneral, development is in accordance with procedures recognized in theart.

Following development of the photoresist coating over the substrate, thedeveloped substrate may be selectively processed on those areas bared ofresist, for example by chemically etching or plating substrate areasbared of resist in accordance with procedures known in the art. For themanufacture of microelectronic substrates, e.g., the manufacture ofsilicon dioxide wafers, suitable etchants include a gas etchant, e.g. ahalogen plasma etchant such as a chlorine or fluorine-based etchant sucha Cl₂ or CF₄/CHF₃ etchant applied as a plasma stream. After suchprocessing, resist may be removed from the processed substrate usingknown stripping procedures.

All documents mentioned herein are incorporated herein by reference. Thefollowing non-limiting examples are illustrative of the invention.

EXAMPLE 1 Particle Additive Preparation

A preferred fluorinated particle additive is prepared as follows:

A reactor vessel is charged with a desired amount of propylene glycolmonomethyl ether acetate (PGMEA) and heated to 80° C. with N₂ purge. Thefollowing monomers (PFPA, ECPMA, TMPTA), cross-linker and initiator(t-amyl peroxypivalate) are mixed in PGMEA at 80 to 90 weight % fluidcomposition in an ice bath. The initiator content is 4% relative to thetotal amount of monomers and cross-liker. The monomers were used in thefollowing weight amounts: 70 weight % pentafluoracrylate (PFPA), 20weight % ethyl cyclopentyl methacrylate (ECPMA), and 10 weight % TMPTA:

That monomer/crosslinker/initiator/PGMEA mixture is then fed into thereactor vessel at a rate of approximately 1 ml/rnin. After the additionto the reactor vessel is complete, the temperature of mixture within thereactor vessel is held at 80° C. for 30 minutes. Then, an additional 2weight % (relative to the total monomers and cross-liner) of initiatoris fed into the reactor, After that addition, the temperature of themixture within the reactor vessel is held at 80° C. for additional 2hours. Thereafter, the temperature of the reactor vessel is permitted tocool to room temperature.

By that procedure, polymer particles were provided that had anumber-average molecular weight (Mn) of 7088 and a weight-averagemolecular weight (Mw) of 19255.

EXAMPLE 2 Photoresist Preparation and Processing

A photoresist composition is prepared by admixing the followingmaterials in the specified amounts:

-   1. Resin component: Terpolymer of (2-methyl-2-adamantyl    methacrylate/beta-hydroxy-gamma-butyrolactone    methacrylate/cyano-norbornyl methacrylate in an amount of 6.79    weight % based on total weight of the photoresist composition;-   2. Photoacid generator compound: t-butyl phenyl tetramethylene    sulfonium perfluorobutanesulfonate in an amount of 0.284 weight %    based on total weight of the photoresist composition;-   3. Base additive: N-Alkyl Caprolactam in an amount of 0.017 weight %    based on total weight of the photoresist composition;-   4. Surfactant: R08 (fluorine-containing surfactant, available from    Dainippon Ink & Chemicals, Inc.) in an amount of 0.0071 weight %    based on total weight of the photoresist composition-   5. Substantially non-mixable additive:

(i) top resin material: a copolymer having 50 mole percent of thefollowing two units and the depicted structure:2-(4,4,4-bis-trifloromethyl hydroxy) butyl methacrylate:t-butylmethacrylate

(ii) intermediate material: 88/8/4 terpolymer of the following structure(88/8/4 mole percent of respective units from left to right in thefollowing structure):

-   6. Solvent component: propylene glycol monomethyl ether acetate to    provide about a 90 percent fluid composition.

The above photoresist composition containing is spin-coated onto siliconwafers, dried on vacuum hotplate to remove soft-plate and then exposedin an immersion lithography process with aqueous immersion fluiddirectly contacting the dried photoresist layers. In that immersionsystem, the photoresist layers is exposed to patterned 193 nm radiationat a dose of 24.1 mJ/cm² through a photomask.

The photoresist layer is then post-exposed baked (such as at about 120°C.) and developed with 0.26N alkaline aqueous developer solution.

To evaluate leaching of resist components after the post-exposure bakeand before development, the immersion fluid can be evaluated for thephotoacid in the resist and its photo-degradation byproducts by LC/massspectroscopy (60 second leaching time tested).

EXAMPLE 3 Additional Photoresist Preparation and Processing

A further photoresist composition is prepared by admixing the followingmaterials in the specified amounts:

-   1. Resin component: Terpolymer of (2-methyl-2-adamantyl    methacrylate/beta-hydroxy-gamma-butyrolactone    methacrylate/cyano-norbornyl methacrylate in an amount of 6.79    weight % based on total weight of the photoresist composition;-   2. Photoacid generator compound: t-butyl phenyl tetramethylene    sulfonium perfluorobutanesulfonate in an amount of 0.284 weight %    based on total weight of the photoresist composition;-   3. Base additive: N-Alkyl Caprolactam in an amount of 0.017 weight %    based on total weight of the photoresist composition;-   4. Surfactant: R08 (fluorine-containing surfactant, available from    Dainippon Ink & Chemicals, Inc.) in an amount of 0.0071 weight %    based on total weight of the photoresist composition-   5. Substantially non-mixable additive in an amount of 0.213 weight %    based on total weight of the photoresist composition. The    substantially non-mixable component contained the following two    distinct top material and intermediate material:

(i) top resin material: a copolymer having 50 mole percent of each ofthe following two units and the depicted structure:

(ii) intermediate material: 25/25/20/30 tetrapolymer of the followingstructure (25/25/20/30 mole percent of respective units from left toright in the following structure):

-   6. Solvent component: propylene glycol monomethyl ether acetate to    provide about a 90 percent fluid composition.

This photoresist composition is processed by the same procedures asdescribed in Example 2 above.

EXAMPLE 4 Additional Photoresist Preparation and Processing

A further photoresist composition is prepared by admixing the followingmaterials in the specified amounts:

-   1. Resin component: Terpolymer of (2-methyl-2-adamantyl    methacrylate/beta-hydroxy-gamma-butyrolactone    methacrylate/cyano-norbomyl methacrylate in an amount of 6.79 weight    % based on total weight of the photoresist composition;-   2. Photoacid generator compound: t-butyl phenyl tetramethylene    sulfonium perfluorobutanesulfonate in an amount of 0.284 weight %    based on total weight of the photoresist composition;-   3. Base additive: N-Alkyl Caprolactam in an amount of 0.017 weight %    based on total weight of the photoresist composition;-   4. Surfactant: RO8 (fluorine-containing surfactant, available from    Dainippon Ink & Chemicals, Inc.) in an amount of 0.0071 weight %    based on total weight of the photoresist composition-   5. Substantially non-mixable additive in an amount of 0.213 weight %    based on total weight of the photoresist composition. The    substantially non-mixable component contained the following two    distinct top material and intermediate material:

(i) top resin material: a 70/30 copolymer of the following structure(70/30 ole percent of respective units from left to right in thefollowing structure):

(ii) intermediate material: 25/25/20/30 tetrapolymer of the followingstructure (25/25/20/30 mole percent of respective units from left toright in the following structure):

-   6. Solvent component: a 50:50 v/v ethyl lactate:propylene glycol    monomethyl ether acetate blend to provide about a 90 percent fluid    composition.

This photoresist composition is processed by the same procedures asdescribed in Example 2 above.

The foregoing description of the invention is merely illustrativethereof, and it is understood that variations and modifications can beeffected without departing from the scope or spirit of the invention asset forth in the following claims.

What is claimed is:
 1. A method for processing a photoresistcomposition, comprising: (a) applying on a substrate a photoresistcomposition comprising: (i) a first resin, (ii) a photoactive component,and (iii) a second resin and a third resin that are substantiallynon-mixable with the (i) one or more resins, and the first resin, secondresin and third resin are each distinct from each other; and (b)immersion exposing the photoresist layer to radiation activating for thephotoresist composition.
 2. The method of claim 1 wherein the second andthird resins comprise photoacid-labile groups.
 3. The method of claim 1wherein the second and third resins comprise fluorine substitution. 4.The method of claim 2 wherein the second and third resins comprisefluorine substitution.
 5. The method of claim 1 wherein the second andthird resins have differing relative hydrophobicities.
 6. The method ofclaim 1 wherein the second and third resins comprise (i) a top materialand (ii) an intermediate material, and the applied photoresistcomposition forms a layer with a substantial portion of the first resincloser to the substrate than a substantial portion of the second resin,and a substantial portion of the second resin is closer to the substratethan the third resin.